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TPS61088: reverse current

matianfu
Intellectual 500 points
Part Number: TPS61088


TPS61088 has forced PWM mode allowing current to flow in the reverse direction. We plan to utilize this feature to charge a Lithium Ion capacitor (LIC), which is a hybrid type supercapacitor (500~1000F, or 200-400mAh, @ 2.5 to 3.8V).

The capacitor is connected at Vin. Vout is set to around 8.4V. In normal operation, Vout is directly connected to a 9V or 12V rail, and the capacitor is expected to be charged by the reverse current. When the capacitor is fully charged, the TPS61088 is switched to PFM mode. When that 9V/12V power rail fails, TPS61088 should work as a backup power source and output 8.4V. The capacitor may work to as low as 2.2V and minimum Vin of TPS61088 is 2.7V, so pre-charge is required.

Question:

1. any problem with such a design?

2. what is the current limit in the reverse direction?

  • 0
    TI__Mastermind 34231 points

    Hello Matianfu,

    That is an interesting idea.

    1. The main concern I came up first is the reverse current tolerance of TPS61088. I checked this device database and found no test data of reverse current. As this device is designed as a boost converter so our ATE didn't consider the reverse current as a test item. That means the charging current tolerance cannot be promised.

    2. Sorry I don't have this data.

    It's better to use a BQ charger device.